The current state of the art apparatus for detecting sea mines from air utilizes either a passive multi-spectral electro-optical (EO) system or an active imaging Laser Imaging, Detection and Ranging (LIDAR) system. With passive EO systems, mine-like objects (MLOs) are detected through imaging changes in the water leaving radiance signal, and such systems can only be used in daylight conditions. Active imaging LIDAR systems employ a pulsed laser transmitter source to direct a laser pulse at the ocean. A detector is then utilized to measure the return signals (both time of flight and intensity), and the variation in the return signals with respect to the background are used to detect the presence of MLOs. Unlike passive EO systems, active imaging LIDAR systems can be operated during day time and night time.
Both passive EO and active imaging LIDAR systems have difficulties in detecting sea mines located at or just beneath the ocean surface. In the case of passive EO systems, surface and floating mines can act as spectral reflectors of the down welling solar irradiance, presenting the same spectral signature as glint. In the case of active imaging LIDAR systems, it is generally not possible to separate the large surface reflection (glint) from the signal generated by surface and near surface sea mines. Basically, glint effects can cause a reduction in detection performance against surface and near surface sea mines for both passive EO and active LIDAR systems.